Begin by bringing a large pot of salted water to a boil. Add the fettuccine pasta and cook according to the package instructions until al dente. Once cooked, reserve about 1 cup of the pasta water, then drain the pasta and set it aside.
In a blender or food processor, combine the ripe avocados, garlic, lemon juice, and milk (or almond milk). Blend until smooth and creamy. If the mixture is too thick, add a little reserved pasta water until you reach your desired consistency.
With the blender running, slowly add the shredded gouda cheese and chopped basil to the avocado mixture. Blend until well combined and creamy. Taste the sauce and season with salt and pepper as needed.
In a large mixing bowl, combine the cooked fettuccine pasta with the creamy avocado and gouda sauce. Toss gently to coat the pasta evenly. If the sauce is too thick, add more reserved pasta water, a little at a time, until you achieve a smooth, luscious coating.
Once everything is combined, stir in the toasted pine nuts for added crunch. Serve the pasta warm, garnished with additional fresh basil and a sprinkle of crushed red pepper flakes if desired.
